1. Field of the Invention
The present invention relates to an automatic optical measuring apparatus which is designed to automatically process tips of an optical fiber held in a holder, connect the optical fiber to a measuring system which performs optical measurement of the optical fiber, and carry out optical measurement.
2. Description of Related Art
Conventionally, when performing optical measurement, e.g., measurement of a transmission loss of a jacketed optical fiber comprising at least one optical fiber provided with a jacket, the jacketed optical fiber to be subjected to the measurement is first held in a holder, then a tip processing such as a jacket removing, cleaning, and cutting is performed manually on the jacketed optical fiber. After that, the holder is set on a specified butting device, the tip of the optical fiber is butt-connected to a measuring system through a dummy fiber by the butting device, and the optical measurement such as the measurement of a transmission loss is performed.
There are, for example, the cutback method and the backscattering method as known optical measurement methods for optical fibers.
In the cutback method, one end of the optical fiber to be measured is butt-connected to a light source of measuring light via a dummy fiber, then an output P.sub.1 of the measuring light emitted from the other end of the optical fiber to be measured is measured using an optical measuring means such as a power meter.
Next, the optical fiber to be measured is cut in the vicinity of a point of connection to the dummy fiber to separate it into a short optical fiber remaining on the dummy fiber and a long optical fiber remaining on the optical measuring means, and an output P.sub.2 of the measuring light emitted through the cut section of the short optical fiber on the dummy fiber is measured again using the optical measuring means.
In the subsequent step, 10.multidot.log(P.sub.1 /P.sub.2) is calculated based on the two measured values P.sub.1 and P.sub.2, and a transmission loss (dB/km) in the longer optical fiber is determined by dividing the calculated value 10.multidot.log(P.sub.1 /P.sub.2) by the length of the long optical fiber that has remained after the cutoff.
The backscattering method is a measuring method which utilizes a phenomenon in which the measuring light entering the optical fiber to be measured returns due to the Reyleigh scattering. An OTDR (optical time domain reflectometer) is in practical use as a device for carrying out the method. In the OTDR, the light source of the measuring light is connected with the optical fiber to be measured via a directional coupler, and a display unit for displaying the intensity of scattered light is also connected to the directional coupler.
The method is advantageous in that it makes it possible to determine a local transmission loss or reflection related to the optical fiber to be measured. More specifically, when the measuring light is emitted from the light source into one end of the optical fiber, the transmission loss can be determined from scattered light which is returned due to back scatter among the light which is scattered while it is transmitted through the optical fiber, and also a place to which the scattered light returns can be identified from a time delay of the scattered light.
When performing such optical measurement of the optical fiber, in a series of steps from holding the optical fiber in the holder to the optical measurement, the holder holding the optical fiber must be handed manually from a step to the subsequent step. For this reason, when performing optical measurement of each optical fiber of an optical fiber cable or the like comprising many optical fibers, the work unavoidably becomes extremely complicated and the measurement takes much time because the series of steps is repeated for each single optical fiber.